The present invention relates to a structure for separating oil, or refrigeration oil, from the refrigerant gas discharged into a discharge chamber of a refrigerant compressor which forms a part of refrigerating cycle of a vehicle air conditioning apparatus.
This type of oil separating structure is disclosed by Japanese Unexamined Patent Publication No. 10-281060. As disclosed specifically on pages 6 to 9 of the reference and FIGS. 1 and 2 thereof, the oil separation structure separates by centrifugal action oil from the discharge refrigerant gas containing therein such oil by introducing the discharge refrigerant gas through an introduction passage into a separation chamber having a cylindrical inner surface and then turning the discharge refrigerant gas in the separation chamber along the cylindrical inner surface. By so separating the oil from the refrigerant gas, the amount of oil which flows out from the refrigerant compressor to an external refrigerant circuit is reduced, and therefore, deterioration of the heat exchanger efficiency which is caused by adhesion of oil to heat exchanger such as a gas cooler and an evaporator in the external refrigerant circuit is prevented.
However, when the introduction passage is formed with a small cross-sectional area, the introduction passage serves as a throttle regulating the flow, thereby increasing the pressure loss of the discharge refrigerant gas, with the result that the performance of the refrigerant compressor is decreased. When the cross sectional area of the introduction passage is set relatively large, on the other hand, the streamline of the discharge refrigerant gas flowing from the introduction passage into the separation chamber is disordered, and the relatively large-sized opening of the introduction passage in the cylindrical inner surface prevents the discharge refrigerant gas from turning in the separation chamber, thus inviting a reduced oil separating capacity. That is, in the prior art structure of the above reference, it has been difficult to satisfy both the maintenance of the desired operating capacity of the refrigerant compressor and the successful oil separation.